To the Editor.—Dr Boushey and colleagues1 report an increased risk of coronary artery disease in people with increased plasma homocysteine levels and suggest that this risk may be reduced by both supplementation and food fortification with folic acid. The dangers of these suggestions prompt us to point out the following.The quoted incidence of pernicious anemia of one in 5000 in a 1985 Mayo Clinic study2 is a marked underestimation because that study based the diagnosis of pernicious anemia on anemia and/or typical neurologic manifestations. Many patients with cobalamin (vitamin B12) deficiency have no anemia and no classical neuropathy. Rather, they may have "dementia" usually ascribed to aging.3 In 1992, Pennypacker et al4 described low cobalamin and/or increased homocysteine and methylmalonic acid serum levels in 14.5% of elderly outpatients. A more recent study found undiagnosed true pernicious anemia in 3% of elderly outpatients or